Field of the Invention
The invention relates to microwave circuits and in particular to a stripline microwave power divider having a wide bandwidth.
Microwave power dividers may be classified in two general categories, namely, corporate and series tapped. Corporate consists of any branching arrangement starting from a single input where the outputs are further subdivided at each division. The path length and phase length to all outputs are governed by the coupling arrangement. As a consequence, a corporate arrangement is complicated. There is also a problem with consistency or uniformity between adjacent outputs because of the inherent difficulty to render the coupling arrangements completely uniform.
In a tapped arrangement a single carrier is tapped along its length with individual outputs. Path length and phase length can be effectively preserved by appropriate spacing of the taps. These arrangements therefore tend to be simpler and more consistent than corporate power dividers.
A common series tapped divider 10, shown in FIG. 1, employs a waveguide 12 having slots 14 located in sidewall 16 and portions of the top and bottom walls 18 and 20. An input signal 22 propagates along the main waveguide 12 and radiates at each slot 14. Taps 24 in the form of slot enclosing output waveguides 26 mate with the main waveguide 12 and enclose the slots 14 to thereby provide power division. The divider is simple and a wide range of couplings is available, but it affords no isolation between outputs.
A known isolated version of the slotted divider 30 is illustrated in FIG. 2. In the arrangement, the input 32 is divided between a pair of main slotted waveguides 34 by a four port coupler 36, output ports 38 of which feed the main waveguides 34. One input 40 of the coupler 36 carries the input signal 41 and the isolated port 42 of the coupler 36 is terminated. Terminal ends 44 of the main waveguidse 34 are appropriately terminated. The main waveguides 34 have adjacent pairs of slots 46 enclosed by corresponding pairs of proximate output waveguides 48. The split input signal 41 from each main waveguides 34 is recombined in the output coupler 50. A terminal output waveguide 52 connected to a corresponding coupler 50 carries the divided power signal to the output 53. Terminations 54 are provided for the unused port of each coupler 50. The arrangement in FIG. 2 is complex, heavy and expensive to fabricate and the bandwidth is limited.